The invention relates to a method for removing silicone oils from sludge wastes generated by a silicone manufacturing plant. In particular, the invention relates to a method for removing silicone oils and volatile organic compounds from waste water treatment plant sludge.
Removal processes for hydrocarbon oils from refinery sludge are known. For example, U.S. Pat. Nos. 5,288,391 and 5,690,811 disclose using a solvent from a refinery unit to extract oils from sludge. However, the oil being removed is typically hydrocarbon oil. Although the extraction process may work on silicone oil sludge, potential environmental liabilities may result. Further, using a solvent previously used at a silicones manufacturing plant is not believed to be possible because the solvent may already contain high levels of silicone oils and thus may not extract oils. Therefore, fresh solvent would be needed for extraction.
Another extraction process is set forth in U.S. Pat. No. 5,271,851, which discloses a process for filtering sludge, washing the sludge with a solvent, and steam stripping the sludge to remove petroleum oils. In another process, an aerobic biomass can be used to degrade the hydrocarbon oils, as disclosed in U.S. Pat. No. 5,207,912. However, silicone oils are much more difficult to degrade. U.S. Pat. No. 5,269,906 discloses an extraction process that involves centrifuging an oily sludge stream with about 5% solids to remove the water and free oil. This step is followed by heating, for example, by indirect heat exchange to remove all of the water and oils resulting in typically bone-dry solids. This process attempts to recover all oil for reuse, and does not focus on the state of the solids remaining.
Thus, a need exists for the treatment of the solids that remain after recovery and extraction processing.